This invention relates to telephone communication systems and more particularly to systems including a keyboard and a display device which can communicate by way of a telephone line.
Devices whereby the individuals having hearing impairment can use voice grade telephone lines are in existence. The teletypewriter is one such system. Another such system is described in a U.S. Pat. No. 3,746,793 wherein a keyboard entry terminal generates character codes which are transmitted to voice grade telephone lines through an acoustic coupler with the telephone receiver cradled thereon. An ordinary television receiver is connected to the terminal to display the operator's message as it is typed. At the receiving terminal, an acoustic coupler is used and the signals received are decoded and displayed on a television receiver.
In another U.S. Pat. No. 3,896,267, there is described a system similar to the one in U.S. Pat. No. 3,746,793 wherein a switch is used for determining whether the diode matrix will encode keyboard entrys in BAUDOT or ASCII codes.
The basic drawback to the systems described in these patents and other similar such systems, is that they are expensive and they are not portable. While the desire for the hearing impaired to communicate over a telephone may be sufficiently great so that the expense of a system, which includes a teletypewriter or a television receiver, is not the real deterrent, the fact remains that with the prior art systems, the hearing impaired can only make and receive telephone calls at the location of the equipment which is fixed because of size and weight. It should be apparent that this constitutes a definite restriction on the ability of the hearing impaired to travel. Also, if help is required and the individual is at the location of a telephone which is not equipped with the indicated system, he could not use a telephone to obtain assistance.